Multi-band radio frequency communication is common to many varieties of audio, video and/or data communication technologies, such as television, telephone, radio and data devices having RF (radio frequency) receivers and/or transmitters. Such data communication technologies may be mobile or fixed, wired or wireless, terrestrial, airborne or satellite, and/or uni-directional or bi-directional. Thus, improvements in multi-band radio frequency communication may improve many related technologies.
FIG. 1 illustrates a functional block diagram of a conventional multi-band RF front-end 100 for multi-band radio communication devices operating in the very high frequency (VHF) and ultra high frequency (UHF) radio frequency ranges. RF signals in the VHF range or meter band have frequencies from about 30 MHz to about 300 MHz and wavelengths ranging from 10 meters to 1 meter. RF signals in the UHF range or decimeter band range have frequencies from about 300 MHz to about 3 GHz with wavelengths of 10 decimeters to 1 decimeter.
RF front-end 100 comprises common or shared multi-band antenna 105, VHF filter 110, UHF filter 115, VHF low noise amplifier (LNA) 120, UHF LNA 125, VHF balun 130, UHF balun 135 and tuner 140. Shared antenna 105 is configured to receive signals in both the VHF and UHF bands. VHF filter 110 and UHF filter 115 filter out signals in frequency ranges other than the VHF and UHF ranges to output filtered VHF signal 145 and filtered UHF signal 150, respectively. VHF and UHF LNAs 120, 125 electronically amplify filtered VHF and UHF signals 145, 150 to output amplified VHF and UHF signals 155, 160, respectively.
VHF and UHF baluns 130, 135 couple VHF and UHF LNAs 120, 125 to tuner 140. VHF and UHF baluns 130, 135 are coupled to VHF and UHF LNAs 120, 125 by unbalanced singled-ended signal lines and are coupled to tuner 140 by balanced (e.g., impedance matched) differential signal lines. VHF and UHF baluns 130, 135 receive amplified VHF and UHF signals 155, 160 on unbalanced single-ended lines and output the received signals to tuner 140 as balanced VHF and UHF differential signals 165, 170. Tuner 140 selects or passes incoming VHF and UHF signals having desired frequencies for further processing (e.g., amplification, conversion, etc.) in tuner 140 and/or a downstream receiver (not shown).
RF front-end 100 duplicates LNAs 120, 125 and baluns 130, 135, even though VHF and UHF signal paths share antenna 105. Additionally, LNAs 120,125 are positioned after VHF and UHF filters 110, 115. Filters 110, 115 generally comprise surface acoustic wave (SAW) filters. Although SAW filters reliably filter out unwanted frequencies through electromechanical signal conversions, SAW filters often exhibit considerable insertion loss or signal attenuation (e.g., approximately a 3 dB loss). Additionally, splitting a received signal between shared antenna 105 and each of VHF and UHF filters 110, 115 may cause further attenuation. Attenuated signals may be problematic with respect to noise and receiver sensitivity, particularly in a high noise environment.